1. Field of the Invention
Present embodiments relate generally to a closure for a pressure vessel or pipe. More specifically, but not by way of limitation, present embodiments relate to a relief structure for a lip seal utilized with a closure mechanism for a pressure vessel or pipe.
2. Description of the Related Art
Closures for pressure vessels and pipes typically utilize a round door or head adapted to fit in the aperture of a body or hub. The hub is connected to a vessel or pipe system or other structure which is typically pressurized. The door or head is lockingly engaged to the hub when in the closed position so that the system or vessel may be pressurized without unknowingly allowing for opening of the head from the hub.
A bore or aperture of the hub has an inner circumferential groove for supporting a portion of a locking member. The door has a locking ring proximate a circumferential portion of an outer surface of the door wherein the locking ring is engaged to cooperate with the groove about the aperture after the door is closed and seated in the aperture. The locking ring is typically biased by a band, ring or segment which is caused to expand or contract, causing the same expansion or contraction of the locking ring to lock or unlock the head from the hub. The locking ring may be formed of one or more segments or may be a unitary structure.
Some closure mechanisms for pressure vessels utilize a seal between the head and the hub in order to inhibit leakage of pressurized fluid from the inside of the closure to the outside. Additional to this point, some seals are designed to be oversized so as to provide and improve the seal between the head and the hub. In certain embodiments, the closure is oriented for use on a vertical pipe such that the head is in a horizontal plane and the weight of the head aids to retain the head against or within the hub. In these embodiments, where a seal is used, it is common for seals to incur damage due to the continuous weight of the head pressing the seal against the hub. In alternate embodiments where the head is in a vertical plane, the head may be so tightly locked in the hub so as to damage the seal. When the seal is oversized, it is possible that the seal may carry much of the load of the head. Over time, this causes damage to the seal and therefore, may result in leakage at the closure.
It would be desirable to overcome these and other deficiencies and provide structure which compensates for the problems associated with overloading of a lip seal.